1. Field of the Invention
This invention relates to an improved process for making an elastomer for use in manufacturing printing belts for use in band printers, and a prepolymer used in the process.
2. Description of the Prior Art
In band printers, a great deal of stress is applied to the drive band or belt. It is therefore necessary that the band be made of a strong, durable material which is also flexible.
In particular, for such a belt, or any type belt some of the most important properties are flex life, tear resistance, cut tear propagation, low to medium tensile modulus and an "A" durometer of about 90. In the past, in order to achieve good flex and tear properties, other properties were degraded. The result is a greater likelihood of breakage in strenuous use and hostile environments.
One of the more successful prior art compositions heretofore used has been Adiprene L-100, a polytetramethylene ether glycol ("PTMEG") reacted with, 4, 4'methylene-bis-(2-chloroaniline) ("MOCA") which produces an elastomer. Both the PTMEG and MOCA are commercially available products. However, this reaction product has two significant disadvantages. One disadvantage is that the typical service life of the Adiprene L-100/MOCA band is about 6000 hours. The other disadvantage is that it has been found that MOCA is a likely carcinogen. It may therefore be undesirable to continue working with MOCA-cured elastomers.
A substitute elastomer which has been used is a urethane elastomer from the Hysol Division of Dexter Corporation designated RU 2028/HDO 121. RU 2028 is also a PTMEG and HDO 121 is a dianthranilic diester. These components, i.e., the RU 2028 HDO 121, are reacted together to produce the substituted elastomer. However, bands manufactured from this elastomer did not have the necessary strength for use as printing belts in band printers.
It is believed that there are currently no compositions available which exhibit superior processing parameters and properties to the Adiprene L-100/MOCA composition, and are cost effective to produce.